Porter and Pale Ale were more widely brewed in Europe than people realise. Almost certainly it was an attempt by a local brewer to cash in on the market for imported British beers.

If you look at the old Dutch newspaper ads I've been posting you'll see that all sorts of British beers were imported into Holland: Porter, Stout, Pale Ale, IPA, Burton, Mild and Scotch Ale. Pretty much the full set of what was brewed in Britain at the time.